A.C. Franke

Maize-grain legume intercropping for enhanced resource use efficiency and crop productivity in the Guinea savanna of northern Ghana

Highlights • Productivity of different intercropping patterns was tested in Guinea savanna of northern Ghana.• Land Equivalent Ratios in intercropping systems are greater under low soil fertility conditions.• Competitive balance between intercrops in poor fields leads to greater Land Equivalent Ratios.• Within-row maize-legume intercropping is more productive than distinct row systems.• Radiation use efficiency is higher in intercrops than in sole crops.

Sustainable intensification through rotations with grain legumes in Sub-Saharan Africa: A review

Highlights • We retrieved 44 publications and 199 observations comparing continuous cereal with grain legume-cereal rotation in SSA.• Cereal after legume yielded on average 0.49 t grain ha−1 or 41% more than continuous cereal.• Sustained residual benefits of legumes with large N applications indicate the importance of non-N effects.• Relevant non-N effects include improved P availability, changes in SOM, and in pest, disease and striga pressure.

Poor farmers - poor yields: socio-economic, soil fertility and crop management indicators affecting climbing bean productivity in northern Rwanda

Climbing bean is the key staple legume crop in the highlands of East and Central Africa. We assessed the impact of interactions between soil fertility characteristics, crop management and socio-economic factors, such as household resource endowment and gender of the farmer, on climbing bean productivity and yield responses to basal P fertiliser in northern Rwanda. Through a combination of detailed characterisations of 12 farms and on-farm demonstration trials at 110 sites, we evaluated variability in grain yields and responses to fertiliser. Grain yields varied between 0.14 and 6.9 t ha −1 with an overall average of 1.69 t ha −1 . Household resource endowment and gender of the farmer was strongly associated with climbing bean yield, even though these were partly confounded with Sector. Poorer households and women farmers achieved lower yields than wealthier households and male farmers. Household resource endowment and gender were likely to act as proxies for a range of agronomic and crop management factors that determine crop productivity, such as soil fertility, current and past access to organic manure and mineral fertiliser, access to sufficient quality staking material, ability to conduct crop management operation on time, but we found evidence for only some of these relationships. Poorer households and female farmers grew beans on soils with poorer soil fertility. Moreover, poorer households had a lower density of stakes, while stake density was strongly correlated with yield. Diammonium phosphate (DAP) fertiliser application led to a substantial increase in the average grain yield (0.66 t ha −1 ), but a large variability in responses implied that its use would be economically worthwhile for roughly half of the farmers. For the sake of targeting agricultural innovations to those households that are most likely to adopt, the Ubudehe household typology – a Rwandan government system of wealth categorisation – could be a useful and easily available tool to structure rural households within regions of Rwanda that are relatively uniform in agro-ecology.

Participatory research to close the soybean yield gap on smallholder farms in Malawi

Soybean yields on smallholder farmers’ fields in Malawi are constrained by poor soil fertility, limited application of external inputs and poor crop husbandry. We tested crop management practices through on-farm experimentation and participatory technology evaluation. Two agronomic soybean trials were established in 2009 and 2010 in three contrasting agro-ecologies resulting in 72 replications per trial. Treatments in the first trial included several combinations of inoculation with Bradyrhizobium japonicum, inorganic fertiliser application and compost manure. In the second trial, farmers tested an improved variety, optimal weeding regime, increased plant population and chemical pest and disease control. A combination of inoculation, inorganic fertiliser (10 N, 8 P, 20 K in kg ha−1), and 6 t ha−1 compost manure increased yields from 0.86 t ha−1 under farmers’ practice to 1.56 t ha−1 and resulted in average profits of US

N 2- fixation and N contribution by grain legumes under different soil fertility status and cropping systems in the Guinea savanna of northern Ghana

222 ha−1. Increased plant populations and biocide spraying also resulted in substantial yield increases. Inoculation and increased plant population resulted in an average value to cost ratio (VCR) > 2. Low investment costs make inoculants, compost manure and increased plant populations interesting options, whereas adoption of inorganic fertiliser application in soybean may be limited due to high costs and low VCR. The farmers ranked eight technologies in descending order of preference as: (i) early planting, (ii) plant population, (iii) variety choice, (iv) compost manure, (v) weeding, (vi) inoculant, (vii) fertiliser and (viii) spraying. Our participatory research approach demonstrated that there is a wide range of technologies with different levels of human and financial investment costs that smallholder farmers can adopt to enhance their soybean yields and profits.

Decision Support System for Site-Specific Fertilizer Recommendations in Cassava Production in Southern Togo

Highlights • Cropping system and soil fertility effects on N2-fixation were tested in northern Ghana.• More N2 is fixed in sole cropping than intercropping despite comparable %Ndfa.• Poorly fertile fields give limited grain legume benefits despite enhanced %Ndfa.• Partial N balances are unreliable indicators of cropping system sustainability.• Different grain legumes should be targeted to different sites in the Guinea savanna.

Understanding variability in soybean yield and response to P-fertilizer and rhizobium inoculants on farmers’ fields in northern Nigeria

The Quantitative Evaluation of the Fertility of Tropical Soils (QUEFTS) model recommended as a decision support tool for deriving optimal site-specific fertilizer rates for cassava has limited ability to estimate water-limited yields. We assessed potential and water-limited yields based on the light interception and utilization (LINTUL) modelling approach in order to enhance the determination of fertilizer requirements for cassava production in Southern Togo. Data collected in 2 years field experiments in Sevekpota and Djakakope were used. Potential ranged from 12.2 to 17.6 Mg ha−1, and water-limited yields from 10.4 to 14.5 Mg ha−1. The simulated average fertilizer requirements were 121 kg N, 2 kg P and no K ha−1 for a target yield of 9.3 Mg ha−1 at Sevekpota, and 103 kg N, 6 kg P and 175 kg K ha−1 for a target yield of 9.7 Mg ha−1 at Djakakope. The variability of fertilizer requirements was attributed to differences in indigenous soil fertility and water-limited yields. The latter correlated well with rainfall variability over years and sites. Integrating LINTUL output with QUEFTS helped account for location-specific weather seasonal variability and enhanced assessment of fertilizer requirement for cassava production in Southern Togo.